You will also need to replace the steering knuckles to these taller CNC-machined Skyjacker units. These are part of the reason the Skyjacker kit requires a 20-inch wheel. We outfitted the F-150 with BMF wheels and 35x12.50R20 Nitto Trail Grappler tires. The 4-inch setting clears 35-inch rubber, while the 6-inch setting clears 37s.